1. Field of the Invention
The present invention relates to an endoscope with an image guide fiber suitable for autoclave sterilization whose observing capability is not deteriorated by a high pressure/high temperature water vapor when the endoscope is sterilized in an autoclave.
2. Description of the Related Art
Conventionally, medical endoscopes are widely used to observe an internal organ in a cavity by inserting a slender insertion section into the cavity and to perform various kinds of medical treatments using medical instruments inserted through a medical instrument channel when necessary. Further, industrial endoscopes capable of observing and inspecting the flaw, corrosion and the like in the interior of boilers, turbines, engines, chemical plants and the like are widely used in industrial fields.
In particular, the endoscopes employed in the medical field are used to observe internal organs and the like by inserting the insertion sections into the cavity and to apply various kinds of cures and perform various kinds of treatments using treatment instruments inserted into the treatment instrument channels of the endoscopes. Thus, when an endoscope and a treatment instrument, which were used once on a patient, are used again on another patient, they must be rinsed and disinfected after the completion of patient inspection and treatment to prevent infections spreading between patients.
A gas such as an ethylene oxide gas (EOG) and the like and an antiseptic solution are used to disinfect and sterilize these endoscopes and the accessories thereof. As is well known, however, there is a problem that the sterilizing gas is highly poisonous and the sterilization process is therefore complicated. Further, a long aeration time is needed for removing the gas deposited on equipment after sterilization. Further, there is a problem that the equipment cannot be used just after it is sterilized. Furthermore, the adverse effect of the gas on the environment is a problem. In addition, the sterilization process is expensive. In contrast, using an antiseptic solution, presents the problem that the management thereof is troublesome and a large cost is required to dispose of used materials.
To cope with the above problems, recently, autoclave sterilization (sterilization by means of high pressure water vapor) is mainly used to disinfect endoscopes because it does not require a troublesome job and permits the use of the endoscopes just after they are sterilized. Further, the running cost is less expensive. The typical conditions for the autoclave sterilization are stipulated by American standards ANSI/AAMI ST 37-1992 approved by American National Standards Institute and issued by Medical Instrument Development Association. According to the conditions, the sterilizing process is carried out at 132xc2x0 C. for 4 minutesxcx9cin a prevacuum type and at 132xc2x0 C. for 10 minutes in a gravity type. In an ordinary autoclave sterilizing process, the temperature is set to 115xc2x0 C. to 140xc2x0 C. and a pressure is set +0.2 MPa with respect to the atmospheric pressure, while the actual conditions vary in different countries.
However, the high pressure/high temperature water vapor in the aforesaid conditions has the property that it is permeable to a material and adhesive mainly composed of a polymeric material such as rubber, elastomer, resin and the like. In particular, the flexible material such as the rubber, elastomer and the like are generally liable to cause water vapor to pass therethrough. In particular, a silicone rubber material has a very high water vapor permeability.
Consequently, in the conventional endoscopes whose water tight structure is constructed using a silicone rubber O-ring, a silicone rubber adhesive and the like, there is a possibility that a high pressure/high temperature water vapor penetrates into the interiors of the endoscopes in the autoclave sterilization and waterdrops remain in the interiors thereof.
Further, water vapor is also permeable even to a fluorine rubber O-ring, an epoxy adhesive and further to various kinds of other polymeric materials, in addition to the silicone rubber, although their degree of permeability is lower than that of the silicone rubber. That is, to prevent the penetration of the water vapor into the interior of the endoscope in the autoclave sterilization, the airtightness, which is required in the endoscope, is much higher than the water tightness which prevents the penetration of a conventional liquid medicine into the endoscope even if it is immersed in it, the airtightness in the ordinary atmospheric pressure and the like.
Ordinary materials used to make a high pressure/high temperature water vapor unpermeable under the conditions stipulated by the American National Standards are limited only to a material selected from metal, ceramics, glass and crystalline material. A joint means for jointing materials to each other is limited only to a joint method, for example, soldering and so forth in which a joint section is mainly composed of metal, ceramics, glass, and crystalline material.
Note that in the prevacuum type autoclave sterilization, a prevacuum process is employed as a pressure reducing process to penetrate a water vapor into the detailed sections of equipment prior to a sterilizing process. When an endoscope with an insertion section having a curved portion is to be subjected to the prevacuum type autoclave sterilization, it is an ordinary practice to perform the autoclave sterilization while communicating the exterior of the endoscope with the interior thereof to prevent the breakage of the outer sheath tube of the curved portion. As a result, the high pressure/high temperature water vapor passively penetrates into the interior of the endoscope through the communicating portion in the autoclave sterilization.
Further, many of multi-component glasses having excellent processability made of ordinary lens glass material are deteriorated by the high pressure/high temperature water vapor. Consequently, there is a possibility that the lens glass material itself is deteriorated by the penetration of the water vapor into the interior of the endoscope. Thereby, the field of vision deteriorated.
For example, in the eyepiece of the endoscope disclosed in Japanese Unexamined Utility model Publication No. 63-180821, the eyepiece visibility adjustment ring is mounted watertightly through an O-ring so that visibility can be adjusted by moving an eyepiece lens in an optical-axis direction by actuating the eyepiece visibility adjustment ring.
When the endoscope is sterilized in an autoclave apparatus, the high pressure/high temperature water vapor penetrates into the interior of the eyepiece section through the O-ring and reaches the inner surface of a cover glass, the back surface of the eyepiece lens and the end surface of an image guide fiber. Thus, there is a possibility that when the endoscope is taken out and used for observation after it is sterilized, a disadvantage arises in that the endoscope is frosted and seems to be covered with white mist.
When the autoclave sterilization is carried out for a long time or repeatedly, there is a possibility that the observing capability of the endoscope is greatly damaged by the deposition of waterdrops on the inner surface of the cover glass, the surface of a lens, and the end surface of the image fiber glass and by the deterioration of the lens glass.
Further, Japanese Unexamined Patent Publication No. 62-212614 discloses a hard endoscope having a hard insertion section in which an observation optical system including an eyepiece lens is arranged airtightly. However, in this endoscope, the visibility of the eyepiece section cannot be adjusted. Thus, when this arrangement is applied to an endoscope using an image guide fiber, there is caused an disadvantage that visibility is not properly set and observation is obstructed depending upon observers. In the endoscope using the image guide fiber, an eyepiece lens must be accurately focused on the end surface of the image guide fiber from which an image is projected regardless of whether a hard mirror or a soft mirror is used. That is, the endoscope is arranged such that an observer can obtain a best subject image by performing visibility adjustment in accordance with his or her vision.
That is, the arrangement of the hard endoscope disclosed in Japanese Unexamined Patent Publication No. 62-212614 is limited only to the hard endoscope having the hard insertion section which employs a relay lens as an image transfer means which does not need the visibility adjustment of the eyepiece section.
In the hard endoscope, since an optical member such as a lens, a cover glass and the like is bonded to a frame member with the adhesive, it is actually difficult to obtain an effect for shutting off a water vapor having a too much higher pressure and temperature. That is, when autoclave sterilization is performed under the conditions stipulated by the American Standards and the like, a water vapor penetrates into the interior of an observation optical system through the adhesive.
To cope with this problem, in the hard endoscope with a hard insertion section disclosed in DE19631840A1, a housing constituting the shell of the endoscope is composed of metal so far as it is possible as well as the joints between components are airtightly jointed to each other by soldering or the like. With this arrangement, the endoscope can be arranged airtightly into which no high pressure/high temperature water vapor penetrates from an autoclave through the shell thereof. In the arrangement of the hard endoscope, the focal length of an optical system can be adjusted by moving a lens disposed in the interior of the airtightly-sealed endoscope by deforming a deformable wall region disposed on the shell of the endoscope.
However, in an endoscope whose insertion section has, for example, a curved portion, the outer sheath tube of the curved portion is composed of a polymeric material such as rubber, elastomer and the like which are flexible. Also in the endoscope with the curved portion, a rubber seal member such an O-ring and the like is used to hermetically seal the rotary shaft of an operation lever for curving the curved portion. Further, even in an endoscope without a curved portion to its insertion section, when the insertion section is flexible, a flexible polymeric material is also used as the outer sheath tube of the inserting section.
Therefore, in a soft endoscope with an insertion section at least a portion of which is composed of a soft material, at least a portion of the shell of the endoscope is composed of a polymeric material. Accordingly, it is impossible to perfectly hermetically seal the entire shell thereof airtightly as shown in DE19631840A1. That is, a high pressure/high temperature water vapor gradually penetrates into the interior of the soft endoscope in the autoclave sterilization.
As described above, the arrangement of the endoscope disclosed in DE19631840A1 is limited only to the hard endoscope whose entire shell can be arranged airtightly by using an insertion section composed of metal or ceramics.
Further, in DE19631840A1, the deformable wall region for adjusting the focal length of the optical system, that is, the visibility adjusting operation section is also a portion of the shell of the endoscope. Accordingly, the visibility adjusting operation section must be composed of a metal material or the like into which a water vapor does not penetrate such as a metal bellows or the like, to which a metal thin film and a lever are disposed, to maintain airtightness. Therefore, the operability in the adjustment of the focal length of the optical system is lowered as compared with the operability in the adjustment of the focal length performed by means of the visibility adjustment ring disclosed in Japanese Unexamined Utility Model Publication No. 63-180821.
Further, the deformable wall region must be airtightly jointed as the shell of the endoscope by soldering or the like. In addition, the joints between the other components of the shell of the endoscope must be airtightly jointed by soldering or the like. Thus, there is a problem that not only the assembling of the endoscope is very poor but also when the endoscope is assembled once, it is almost impossible to repair the inner components therein, or readjustment of the visibility adjustment member or the like by removing a portion of the shell.
An object of the present invention is to provide an endoscope suitable for autoclave sterilization including an image guide fiber as an image transmission means whose observing capability is not deteriorated even if it is exposed to high pressure/high temperature water vapor.
Another object of the present invention is to provide an endoscope suitable for autoclave sterilization including an image guide fiber through which an observer can observe the subject image of an observation section which is transmitted through the image guide fiber under best conditions by adjusting the visibility thereof in accordance with his or her vision.
Still another object of the present invention is to provide an endoscope suitable for autoclave sterilization including an image guide fiber which can be easily assembled and repaired.
A further object of the present invention is to provide an endoscope suitable for autoclave sterilization including an image guide fiber which has excellent operability in visibility adjustment.
Briefly, an endoscope of the present invention suitable for autoclave sterilization includes an inserting section having an objective lens section disposed at the extreme end thereof for focusing a subject image and an eyepiece section located at the base end side of the inserting section and including at least an eyepiece lens. An image guide fiber is disposed in the inserting section which is composed of an optical fiber bundle for transmitting the subject image in an observation section focused by the objective lens section, and an eyepiece lens unit is disposed in the eyepiece section, the eyepiece lens unit causing the eyepiece lens to confront the base end surface of the image guide fiber and having a hermetic seal structure whose hermetic seal level is higher than the watertight seal level of the shell of the endoscope. A focus position changing means is disposed at the eyepiece lens unit to change the focus position of the eyepiece lens.